The invention discloses a splicing processing system and a control method of dual master control of the splicing processing system. Two master control boards are used for controlling the whole splicing processing system; the two master control boards can work in an independent working pattern and also can work in a cooperated working pattern. When the two master control boards work in the cooperated working pattern, one master control executes all control work and the other master control is used as a back-up; when the state of the master control for executing all control work is changed, synchronous data are sent to the master control as the back-up, so that the states of the two master controls keep consistent. When the master control for executing all control work has faults, the master control as the back-up can take over the control work at any time. and the control work is seamlessly engaged, so that the stability and the continuity of the system are improved. When the two master control boards work in the independent working pattern, the two master controls are used for controlling one set of output signal board respectively, and the two sets of output signal boards can correspond to two independent splicing walls; the two splicing walls can be provided with tabletop backgrounds with different resolution ratios and displays and the like, so that the flexibility of the system is increased.